The filter bubble is particularly pernicious when searching for political topics. That's because undecided and inquisitive voters turn to search engines to conduct basic research on candidates and issues in the critical time when they are forming their opinions on them. If they're getting information that is swayed to one side because of their personal filter bubbles, then this can have a significant effect on political outcomes in aggregate.

Interesting study into the very real problem of Google's filter bubble, but do note that the study is performed by DuckDuckGo, a competitor to Google Search (one that I use myself, I might add). That being said, all the results, methodology, and data is freely available, and the code used to analyse the data is available on GitHub.